This application addresses the issue of whether HIV-1 and immune activators in CSF truly reflect brain parenchymal infection. Specifically, the proposal investigates the contribution of the choroid plexus (CP) and meninges. The Aims of the proposal are 1). To determine if the CP is a source of HIV in CSF; 2). To determine the susceptibility and permissivity of CP epithelial and fibroblastoid cells to HIV; 3) Examine CP and meningeal tissues from HIV-infected patients with and without neurological disease; and 4). To determine if the CP represents a significant source of some of the molecules increased in CSF in HIV-infected individuals. These Aims are underscored by a series of appropriate hypotheses and questions to be addressed.